Clarify/adjust assessment stat access.

[FrenjaminBanklin]

Currently anybody with minimal access to a module is able to view all assessment statistics on that module, even historical.

At the very least we should consider moving the ability to view assessment stats from 'minimal' to 'partial', and we should probably also adjust the messaging in the Module Access dialog to clarify what 'assessment stats' means, and potentially encourage the creation of copies first.